Oxidation of benzene to phenol



United States Patent 3,360,572 OXIDATION OF BENZENE T0 PHENOL Charles M. Selwitz, Monroeville, Pa., assignor to Gulf Research & Development Company, Pittsburgh, Pa., a corporation of Delaware No Drawing. Filed Dec. 22, 1964, Ser. No. 420,436 14 Claims. (Cl. 260-621) ABSTRACT OF THE DISCLOSURE Phenol is produced by oxidizing benzene with a gas containing molecular oxygen at a temperature between about 600 and 800 C. in the presence of water and HBr or a compound capable of resulting in the formation of HBr under reaction conditions.

This invention relates to a process for the oxidation of a benzene compound, particularly to a process for oxidizing a. benzene compound to the corresponding phenolic compound with a compound containing molecular oxygen, in the presence of water and a compound selected from the group consisting of HBr and compounds capable of resulting in the formation of HBr under the conditions of the reaction. Examples of compounds that can be oxidized include benzene itself and benzenes containing substituents, such as chloro, nitro, cyano, methoxy, etc. Of these, benzene is preferred as charge. Benzene will be converted primarily to phenol, with only small amounts of diphenyl. The remaining benzenes upon oxidation, in accordance with the defined procedure, will be converted to the corresponding phenol, with the substituent on the benzene charge being present in the phenol obtained.

Any gas containing molecular oxygen, including oxygen itself, can be employed in the oxidation process. The amount of oxygen required will be about 0.02 to about five mols per mol of said benzene compound, preferably from about 0.1 to about 1.0 mol per mol of said benzene compound. Oxygen below the defined amounts will result in no significant amounts of oxidation, while oxygen in amounts above the defined amounts tends to result in overoxidation of the aromatic charge.

To render the reaction selective toward formation of the desired phenol and to moderate the reaction, the same is carried out in the presence of a selected amount of water. The amount of water required will be from about 0.5 to about 50 mols per mol of said benzene compound, preferably from about two to about 20 mols per mol of said benzene compound.

In order to obtain excellent conversion of said benzene compound and excellent yields to the desired phenols, the reaction is carried out in the presence of HBr or compounds capable of resulting in the formation of HBr under the reaction conditions defined herein. I am of the opinion that the effective compound herein is HBr and that any compound that produces HBr under the conditions of the reaction can be employed. Compounds capable of resulting in the formation of HBr, as defined, include brominated hydrocarbons, such as S-bromoacenaphthene, 9-bromoanthracene, l-bromo-l-butene, (l-bromoethyl)benzene, (2-brornoethyl)benzene, Z-bromomesitylene, (3-bromopropyl)benzene, benzyl bromide, 3-bromobutene-1, 4-brornopentyne-2, alpha-bromo-orthoxylene, diphenylbromomethane, cyclopropylbromide, etc., particularly brominated paraffins, such as 2-bromobutane, bromocyclohexane, bromocyclopentane, l-bromodecane, 3-bromodecane, bromoethane, bromo'form, l-bromoheptane, 3-bromohexane, 1-bromo-3-methylbutane, 3- (bromomethyl)heptane, 2-brorno-2-methylpropane, 1,1- dibromoethane, 1,2-dibromoethane, 1,2-dibromobutane,

Patented Dec. 26, 1967 ICC mo-2-butanone, 2-bromo-4-tertiary-butylphenol, 2 -brornobutyric acid, l-bromo-Z-nitroethane, para -bromo-N,N- diethylaniline, 2-bromoethanol, 2-bromoethyl acetate, 2-bromoethylamine hydrobromide, 2-bromoethyl ethyl ether, 3-bromo-3-methylbutyric acid, etc. Preferred compounds are 2-bromo-2-methylpropane, 2-bromo-2-methylbutane, 1,2-dibrornoethane, etc., and homologues thereof. Bromine itself or organic iodine-containing or organic chlorine-containing compounds are not suitable for purposes of the claimed process. The amount of HBr or compound capable of resulting in the formation. of'HBr required is at least about 0.0001 mol. per mol of the benzene charge, preferably about 0.001 to about 0.20 mol per mol of the benzene charge.

The oxidation reaction defined herein must be carried out at a temperature in the range of about 600 to about 800 C., preferably in the range of about 650 to about 750 C. Below this temperature range no appreciable reaction occurs, whereas at temperatures above the defined range overoxidation resulting in the formation of unwanted compounds occurs. Pressure is not critical and can be, for example, from about one to about pounds per square inch gauge, preferably from about 10 to about 20 pounds per square inch gauge.

Under the reaction, conditions defined above, the reaction mixture is in the vapor phase and, accordingly, the reaction mixture is continuously passed through a reactor having a nonreactive surface toward the reaction, such as a calorized surface or a suitable ceramic surface. Space velocities (total volume of vapor per volume of reactor per hour) of about 100 to about 10,000, preferably about 1000 to about 5000 are maintained.

Upon completion of the reaction, the reaction mixture is cooled to a suitable low temperature at which further reaction essentially ceases, for example, a temperature of about 0 to about 70 C., preferably about 20 to about 30 C., and recovery of the desired phenol therefrom is efiected in any suitable manner. Thus, in the case wherein benzene has been converted to phenol, the reaction mixture resolves itself into an upper organic or benzene phase and a lower or aqueous phase. The two phases are separated from each other in any suitable manner, for example, by decantation, and the aqueous phase is extracted with benzene to remove phenol therefrom. The latter extract is combined with the separated organic or benzene phase and the total is subjected to suitable distillation procedures to remove benzene therefrom. The remainder can be subjected to further distillation to recover the desired phenol. The aqueous phase previously recovered from the reaction product contains dissolved therein the hydrogen bromide present in the reaction zone. In a preferred embodiment, the aqueous phase and the recovered benzene can be recycled to the reaction zone.

The process defined herein can further be illustrated by the following:

Example I Into a calorized reactor (one containing an aluminum oxide internal surface) 24 inches high and an internal diameter of one inch, and which was maintained at atmospheric pressure, there was continuously introduced water vapor, benzene vapor, an organic bromide in vapor form and oxygen. The reaction product obtained was cooled to 23 C. and the phenol therein was recovered by extraction and distillation aspreviously defined. The results are tabulated below in Table I.

TABLE I Run No H 1 l 2 l 3 4 5 6 l 7 v 8 l 9 l 10 I 11 12 Catal st DlB D113 D113 DlB D1B DlB DlB DlB tAB tBB tBB tBB .Mols Per Hour of Catalys 0.0043 0.0056 0.0054 0.0058 0.0039 0.0043 0. 0045 0. 0018 0. 0044 0.0053 0. 0027 0.0013 Water, Mols Per Hou.r 10. 2 18. 7 16. 5 17. 3 8. 5 10.3 10.3 4. 4 9. 7 10.0 5.1 5. 3 Benzene, Mols Per Hour 1.0 .35 1. 3 1. 4 O. 94 1.01 1. 08 0.44 0.86 0. 93 0. 47 0.45 Oxygen, Mols Per Hour 0.45 0. 60 0.60 0. 60 0.41 0.41 0.41 0.21 0.41 0.41 0. 21 0. 21 Average Temperature, C. 673 687 739 722 691 714 716 692 690 693 691 690 Highest Temperature, C 682 698 747 733 701 722 724 701 699 706 700 701 Space Velocity (Volume of Vapor Per Volume 0t Reactor Per Hour) 2, 750 4, 830 4, 640 4,780 2, 360 2,890 2, 920 1, 210 2, 600 2, 730 1, 400 1,400 Conversion, Percent 11. 2 7. 5 15. 9 8. 10.6 9.0 11. 21. 6 18. 18.5 25. 0 13.1 Molar Efliciency, Per 40 62 40 61 71 81 75 40 44 40 36 60 DlB =1,2-dibronioetl1ane; tAB =tertiary amyl bromide; tBB =tertiary butyl bromide.

The data in Table I show that the use of 1,2-dibromoethane, tertiary amyl bromide and tertiary butyl bromide in the claimed process resulted in a molar efiiciency of benzene to phenol as high as 81 percent. Even at relatoluene. The results are summarized below in Table III. It can be seen from the data therein that the process defined herein is specific to benzene and cannot effective ly be applied to toluene.

tively high conversion of benzene selectivity to phenol was excellent. The remaining products obtained in the re- TABLE III Run N o 23 24 26 27 28 Catalyst None None None None 1,2-dibrornoethane Moles Per Hour of Catalyst 0 0 0 0 0.002 0. 0033 Water, Mols Per Hour- 5. 8 7. 85 5. 5 5. 5 7. 5. 5 Toluene, Mols Per Hour 1.2 1. 23 0.5 0.5 0.5 0.84 Oxygen, Mols Per Hour.-- 0. 56 1. 34 0. 5 0. 5 0. 5 0. Average Temperature, C- 735 704 735 760 764 758 Highest Temperature, C 741 826 749 793 780 788 Space Velocity (Volume of Vapor Per Volume of Reactor Per Hour)- 1,917 2, 540 1, 638 1, 680 2, 067 1, 770 Conversion, Percent 10. 31. 0 2 2 19 12. 1 Molar Efficiency, Percent to-- Example IV action included biphenyl, carbon dioxide and carbon monoxide.

Example ll Additional runs were made in the same reactor as that employed in Example l. In this instance, however, HBr was employed in place of alkyl bromides employed in Example I. The results obtained are summarized below in Table II and show that HBr is an effective catalyst in the defined process. In addition to phenol, the following compounds were also obtained: biphenyl, carbon m0noxide and carbon dioxide.

In order to show the advantageous effect of an alkyl bromide in the claimed procedure, two additional sets of runs were made at different temperature levels, in each 0 set of which one run was made in the presence of a small to phenol, while at thehigher temperature level the con- TABLE II Run N0 13 14 15 16 17 18 19 20 21 22 Mols Per Hour 01 11B! 0. 0103 0. 0107 0. 0064 0. 0083 0. 0069 0. 0029 0. 014 0. 0115 0. 0049 O. 0138 9.3 9.6 5.8 7.5 6.2 6.4 6.4 8.6 3.7 6.2 0. 86 0. 84 0. 89 0. 85 0. 86 0. 86 0. 87 1. 10 0. 90 0. 87 0. 45 0. 45 0. 45 0. 66 0. 45 0. 45 0. 45 0. 36 0. 59 0. 45 708 685 687 672 679 682 650 711 67 683 Highest Temperature, C 715 689 697 676 684 684 653 715 680 685 Space Velocity (Volume of Vapor Per Volume of Reactor Per Hour) 2, 600 2,640 1,700 2,1 5 1, 780 1,837 1, 777 2, 608 1, 225 1, 744 Conversion, Percent 12.4 9. 7 14. 19. 6 15. 4 l9. 0 9. 0 10. 6 16. 9 14v 3 Molar Efiiciency, Percent 45. 0 34. 4 49. 2 35.1 51.0 50. 0 49.1 44. 4 46. 4 39. 0

Example III Under the conditions described in Example I, the oxidation of toluene was carried out by replacing benzene with version was essentially doubled when 1,2-dibromoethane was present and the molar efiiciency to phenol was im- 5 proved.

TABLE IV Run N .y 29 I 30 i 31 32 Mols Per Hour of 1,2-dibromoethane. None 0.0033 None 0.0037 Water, Mols Per Hour 8. 4 7.9 7. 6. 26 Ben ene, Mols Per Hour. 0.884 0.880 0.933 0. 919 Oxygen, Mols Per Hour 0 44 0.44 0.46 0. 46 Average Temperature, 0.. 738 729 678 681 Highest Temperature, C 744 733 86 Space Velocity (Volume of Vapor 2, 460 2,340 2,117 1,830

Per Volume of Reactor Per Hour).

Conversion, Percent 10.2 20. 9 20. 7

Molar Efficiency, Percent 31.9 40.8 50.0

1 No conversion.

Example V That other alkyl halides and elemental bromine are not effective in the process defined and claimed herein is apparent from an additional series of runs made in accordance with the above and whose data are recorded below in Table V.

TABLE V Run N0 27 28 29 30 Catalyst Mols Per Hour of Catalyst Water. Mols Per Hour 5 0 5 O 5.0 8 3 Benzene, Mols Per Hour 0. 5 0. 5 0. 5 0.95 Oxygen, Mols Per Hour 0.25 0.25 0.25 0.47 Average Temperature, C 690 690 685 H ighest Temperature, C (l 700 693 Space Velocity (Volume of Vapor 1,390 1, 440 1, 390 2,322

Per Volume of Reactor Per Hour) Conversion, Percent 4 16 Molar Efficiency, Percent 38 16 16 containing gas being sufiicient to provide from about 0.02

to about 5 mols of oxygen per mol of said benzene compound, in the presence of about 0.05 to about 50 mols of water per mol of benzene and at least about 0.0001 mol of a compound selected from the group consisting of HBr and a compound capable of resulting in the formation of HBr.

2. A process for oxidizing benzene to phenol which comprises contactingat a temperature of about 600 to about 800 C. in the vapor phase benzene with a gas containing molecular oxygen, the amount of said oxygen containing gas being sufficient to provide from about 0.02 to about 5 mols of oxygen per mol of said benzene compound, in the presence of about 0.05 to about 50 mols of water per mol of benzene and at least about 0.0001 mol' of HBr.

3. A process for oxidizing benzene to phenol which comprises contacting at a temperature of about 600 to about 800 C. in the vapor phase benzene with a gas containing molecular oxygen, the amount of said oxygen containing gas being sufficient to provide from about 0202 4. A process for oxidizing benzene to phenol which comprises contacting at a temperature of about 600 to about 800 C. in the vapor phase benzene wit-h a gas containing molecular oxygen, the amount of said oxygen 5 containing gas being sufficient to provide from about 0.02

to about 5 mols of oxygen per mol of said benzene compound, in the presence of about 0.05 to about 50 mols of water per mol of benzene and at least about 0.0001 mol of an alkyl bromide.

10 5. A process according to claim 4 wherein the alkyl bromide is 1,2-dibromoethane.

6. A process according to claim 4 wherein the alkyl bromide is tertiary butyl bromide.

7. A process according to claim 4 wherein the alkyl 1 bromide is tertiary amyl bromide. v

8. A process for oxidizing benzene to phenol which comprises reacting in the vapor phase at a temperature of about 600 to about 800 C. benzene with about 0.02

to about five mols thereof of oxygen in the presence of about 0.5 to about 50 mols thereof of water and about 0.0001 to about 0.20 mol thereof of a compound selected from the group consisting of HBr and a compound capable of resulting in the formation of HBr.

9. A process for oxidizing benzene to phenol which comprises reacting in the vapor phase at a temperature of about 600 to about 800 C. benzene with about 0.02 to about five mols thereof of oxygen in the presence of about 0.5 to about 50 mols thereof of water and about 0.0001 to about 0.20 mol thereof of HBr.

10. A process for oxidizing benzene to phenol which comprises reacting in the vapor phase at a temperature of about 600 to about 800 C. benzene with about 0.02 to about five mols thereof of oxygen in the presence of about 0.5 to about 50 mols thereof of water and about 0.0001 to about 0.20 mol thereof of a compound capable of resulting in the formation of HBr.

11. A process for oxidizing benzene to phenol which comprises reacting in the vapor phase at a temperature of about 600 to about 800 C. benzene with about 0.02

to about five mols thereof of oxygen in the presence of about 0.5 to about 50 mols thereof of water and about 0.0001 to about 0.20 mol thereof of an alkyl bromide.

12. A process for oxidizing benzene to phenol which comprises reacting in the vapor phase at a temperature of about 600 to about 800 C. benzene with about 0.02 to about five mols thereof of oxygen in the presence of about 0.5 to about mols thereof of water and about 0.0001 to about 0.20 mol thereof of 1,2-dibromoethane.

13. A process for oxidizing benzene to phenol which 50 comprises reacting in the vapor phase at a temperature of about 600 to about 800 C. benzene with about 0.02 to about five mols thereof of oxygen in the presence of about 0.5 to about 50 mols thereof of water and about 0.0001 to about 0.20 mol thereof of tertiary butyl bromide.

14. A process for oxidizing benzene to phenol which comprises reacting in the vapor phase at a temperature of about 600 to about 800 C. benzene with about 0.02 to about five mols thereof of oxygen in the presence of about 0.5 to about 50 mols thereof of water and about 9 0.0001 to about 0.20 mol thereof of tertiary amyl bromide.

References Cited UNITED STATES PATENTS 8/1945 Harman 260-621 2/ 1947 Rust et'al 260619 OTHER REFERENCES LEON ZITVER, Primary Examiner.

H. ROBERTS, Assistant-Examiner.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,360,572 December 26, 1967 Charles M. Selwitz error appears in the above numbered pat- It is hereby certified that t the said Letters Patent should read as ent requiring correction and the corrected below.

Columns 3 and 4, TABLE I, third column, line 4 thereof, for ".35" read 1.35

Signed and sealed this 21st day of January 1969.

(SEAL) Attest:

EDWARD J. BRENNER Edward M. Fletcher, Jr.

Commissioner of Patents Attesting Officer 

1. A PROCESS FOR OXIDIZING BENZENE TO PHENOL WHICH COMPRISES CONTACTING AT A TEMPERATURE OF ABOUT 600* TO ABOUT 800*C. IN THE VAPOR PHASE BENZENE WITH A GAS CONTAINING MOLECULAR OXYGEN, THE AMOUNT OF SAID OXYGEN CONTAINING GAS BEING SUFFICIENT TO PROVIDE FROM ABOUT 0.02 TO ABOUT 5 MOLS OF OXYGEN PER MOL OF SAID BENZENE COMPOUND, IN THE PRESENCE OF ABOUT 0.05 TO ABOUT 50 MOLS OF WATER PER MOL OF BENZENE AND AT LEAST ABOUT 0.0001 MOL OF A COMPOUND SELECTED FROM THE GROUP CONSISTING OF HBR AND A COMPOUND CAPABLE OF RESULTING IN THE FORMATION OF HBR. 